Grub2 can boot with root=UUID but needs an initrd.
Currently it's possible to boot with "root=PARTUUID=" and I'm doing it on my system.
The only culprit is that 'grub-mkconfig -o', '10_linux' script and '/etc/default/grub' does not make the proper input into grub.cfg ;)

Fixing this does not require change in to grub source itself (that part is already done), it requires change in to grub's configs and scripts only. ;)

I think that this enhancement will be well accepted by the people that are willing to boot without an initramfs